EXHIBIT 99.1
                                                                    ------------



                              AMENDED FORM 51-101F2
                           REPORT ON RESERVES DATA BY
                      INTERNAL QUALIFIED RESERVES EVALUATOR



To the Board of Directors of Nexen Inc. (the "Company"):

1.       Company staff and I have evaluated the Company's reserves data as at
         December 31, 2003. The reserves data consist of the following:

         (a)      proved oil and gas reserve quantities estimated as at last day
                  of the Company's most recently completed financial year using
                  constant prices and costs; and

         (b)      the related standardized measure.

         (both (a) and (b) form part of the "FAS 69 Disclosures about Oil and
         Gas Producing Activities" contained in the Company's Supplementary
         Financial Information in its Annual Report on Form 10-K).

2.       The reserves data have been prepared in accordance with:

         (a)      United States' Securities and Exchange Commission (SEC)
                  requirements;

         (b)      generally accepted industry practices in the United States as
                  promulgated by the Society of Petroleum Engineers; and

         (c)      the standards of the Canadian Oil and Gas Evaluation Handbook
                  modified to reflect SEC requirements.

         (collectively, the Nexen Reserves Standards).

3.       The reserves data are the responsibility of the Company's management.
         My responsibility is to express an opinion whether the evaluation was
         carried out in accordance with the Nexen Reserves Standards.

4.       I am not independent of the Company, within the meaning of the term
         "independent" under National Instrument 51-101.

5.       Among other things, with respect to matters regarding royalties,
         operating costs, development plans and costs, abandonment plans and
         costs, and income taxes (where applicable), I have placed reasonable
         reliance on the information and decisions of others in their areas of
         authority, responsibility and expertise within the Company.

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6.       In my opinion, the reserves data has, in all material respects, been
         prepared in accordance with the Nexen Reserves Standards.

7.       Reserves are estimates only and not exact quantities. Estimates of
         economically recoverable oil and natural gas reserves and future net
         cash flows are based on a number of variable factors, assumptions and
         judgements regarding future events. It is believed that the factors and
         assumptions used and judgements made in estimating reserves are
         reasonable based on the information available at the time the estimates
         were prepared. Actual results will vary and such variances could be
         material.

8.       I have no responsibility to update this opinion for events and
         circumstances occurring after the date of this opinion.

9.       I have signed this Form F2 in my capacity as an employee of Nexen Inc.
         and not in my personal capacity.





/s/ Ian R. McDonald
-----------------------------

IAN MCDONALD
NEXEN INC.
MANAGER, CORPORATE RESERVES
CALGARY, ALBERTA

FEBRUARY 3, 2004